Agricultural phosphorus and eutrophication (Work package 2)

Agricultural water protection takes shape in measures incentivized by society and undertaken by farmers to reduce the runoff and leaching loss of nutrients and pollutants to receiving waters. The question the WP2 answers is how to allocate resources between the measures to reach the maximum reduction in phosphorus (P) mediated eutrophication in surface waters.

The answers are sought in four section tasks. The first one addresses the trade-offs in mitigating the particulate and dissolved P loading. It is well known that most commonly used measures to cut down the loading of particulate P, such as permanent wintertime vegetative cover, tend to increase the lossing of dissolved P. We quantify how this process develops over time, driven by gradual vertical stratification of soil P. Based on the process we optimize the tilling frequency to strike a balance between the loading patterns of particulate P and dissolved P.

The second section task scrutinizes the long-term contribution of particulate P to the pool of algal available P in the sediments of receiving waters. This is essential information for the optimal balance of the loading of different P forms. We conduct the laboratory analysis for different source soils by changing the concentrations of sulfate and organic carbon under aerobic and anaerobic conditions and sulfate as well as oxygen concentrations.

The third task section analyzes the costs and effects of a novel, calcium based soil amendment method, structure liming. The fourth task section combines the first three into a dynamic cost-effectiveness analysis. It answers the question, how to optimally combine tilling frequencies and structure lime amendments for soils of varying initial conditions and erosion susceptibilities when we want to curtail the P-mediated eutrophication as effectively as possible with our limited resources

Task 2A: Effects of no-till on dissolved and particulate phosphorus

The Kotkanoja test field with plots under no-till and annual ploughing will be utilised in testing how one-time ploughing of no-till affects surface and subsurface losses of dissolved and particulate Phosphorus.

Participating in the study:

Task 2B: Release of phosphorous from soil in bodies of water

When soil eroded from fields enters the bottom of a body of water it confronts completely different conditions. The amount of phosphorus in the soil that can be released in oxygen-free conditions is examined in laboratory tests.

Quick lime (CaO/Ca(OH)2) can improve aggregate stability of topsoil with a high clay content and reduce phosphorus losses. How do soil characteristics affect the outcome of the treatment? What is the impact on greenhouse gas emissions? This is being studied at the Jokioinen testing area and in laboratory